Wind Turbine Drone Inspection: Q&A

What are the main advantages and benefits of a wind turbine drone inspection?

The use of drones in wind turbine inspection is related to the size of the infrastructure and their access. Due to their considerable height and complexity, wind turbines present difficulties that make inspections challenging.  

The main elements to inspect in a wind turbine are turbine blades; gearboxes; main bearings and shaft; generators; tower, flanges, bolts; foundation, and nacelle. From those, the blades, the nacelle, and the tower must be inspected from the inside and outside.

Visual inspection is one of the leading wind turbine inspection techniques used for the outside. This technique may seem basic but provides much information about the asset's condition if appropriately applied. This inspection can be done from the ground using a telescope or telephoto lens or by checks at height through rope access techniques or a lifting platform. Both methods have helped in the past years to determine those components' condition; however, in the first case, with low accuracy or precision, and in the second case compromising the speed and safety.

Wind turbine drone inspection is the most convenient of both methods; it is faster, more precise, and increases overall safety.

How are wind turbines inspected using drones?

Due to the increasing size of the wind turbines and the blades, this has become one of the most critical components. It is an element highly exposed to environmental conditions and made of fiberglass and composite resins, which increase their exposure. Any slightest defect in a blade has a direct impact on energy production.

Wind turbine blade inspection must be carried out from the inside and the outside, looking in each case for different issues. On the interior will be more structural defects coming from the design or manufacturing process, and from the outside will be more related to erosion and environmental exposure, like surface cracks, leading-edge erosion; lightning strikes; bird strikes; delamination, or edge splits.

A similar process happens with the tower and the nacelle. Both need to be inspected from the inside and the outside, but in this case, looking more for general corrosion or structural damage, also using visual inspection. In the tower case, it could also be interesting to test the welds looking for any sign of fatigue, especially on the primary top flanges. We can find solutions to do it from the outside; however, it is today much more effective to do it from the inside.  

The optimal method for inspecting a wind turbine's exterior is through cutting-edge wind turbine drone inspection technology. It may be limited by the weather condition, wind, and visibility, but that also affects inspections at height through rope access techniques or lifting platforms. Using drones increases personnel safety exponentially as we only need a pilot on the ground and nobody else around.

The process is straightforward. Once you set the drone and finalize the verification routines before starting the flight and ensuring all the safety rules are in place, the wind turbine will need to stop and remain out of service during all the inspection time, especially if we are going to inspect the blades. During the inspection process, it may be necessary, in some cases, to rotate the wind blades to check all sides; that can be done by the site personnel or the inspection team mobilized. 

The flight duration can go from 15 to 30 minutes, more or less the course of the batteries, which will depend on the time flying and the weight carrying on, which is also related to the inspection equipment installed: high resolutions and thermographic cameras, LiDAR systems, etc.   

How often should wind turbines be inspected?

Each manufacturer has their maintenance recommendations: gearbox, blades, generators, etc. Based on that and the experience of the owners and maintenance suppliers, you can set a maintenance plan and build or recommend a turbine inspection plan from there and the knowledge of the inspection companies. A good inspection plan aims to act as a "preventive maintenance" routine. As its name indicates, it means anticipating failure, thus preventing it and thereby avoiding production losses due to poor planning of maintenance work or incapacity to adapt to failures that may appear.

Drone inspection services for the outside wind inspection process are more effective, precise, safe, and cost-effective. It is highly recommended to make one full inspection a year and, only in those cases where damage or defects have been detected, perform additional inspections, depending on the type of defect and severity.

How do you ensure the captured data's reliability, accuracy, and quality?

When using drones, there are two key factors to ensure the reliability and accuracy of the captured data: the flight and the equipment used, and both are connected.

The flight needs an experienced pilot, even when using drones with autonomous flight capability. Apart from being in charge of the execution and safety of the flight plan, the pilot has to make sure that the optimal conditions of distance, image center, movement, and visibility, are given to proceed to capture the data.

On the other side, the inspection equipment and the sensors must be the most appropriate and offer the highest quality for this type of inspection.  You will need a smart camera with exposure and dynamic aperture adjustment and a 0.3 mm/pixel high resolution for good visual capture data. This will be on the high good practice standards. The same applies to any other sensor like LiDAR or thermographic cameras.

How is this data processed? 

Once the flight is finished, the ground team will perform a pre-quality check to ensure that all the data captured is valid and nothing is missing. After this field routine, all the data capture will be sent to the Cloud data management system, where the data processing will start. 

In the case of the images, this process will include two main stages. First, the data will be processed by Artificial intelligence software trained by blade design and inspection engineers. This algorithm will detect most defects and perform a  damage categorization in the case of blades following EPRI blade defect white paper. Once this process is finished, all these defects and classification reports will be individually reviewed and validated by the Human-in-the-Loop team of experts. 

Benefits of using Drones and AI Systems:

• Wind turbine drone inspection is faster than conventional methods through rope access techniques or lifting platforms.
• It provides better data quality than using a telescope or telephoto lens from the ground.
• Increases safety, as no personnel inspection at height is required.
• Our wind turbine inspectors provide highly tailored services and deliver exceptional efficiency in data collection times.
• Sensors are quickly interchangeable, depending on the inspection scope. 
• Our drones can fly onshore and offshore wind farms in various weather conditions.
• It is cost-efficient due to the speed and less human involvement during the data capture.
• It provides high-resolution images for accurate defect detection & location.
• It is highly reliable, bringing advanced AI-based data analytics & reporting, trained by the most expert blade engineers and drone inspectors.

Applus+ Wind Services cover a wide array of technical expertise and unbiased advice related to wind engineering, wind consulting, quality assurance, quality control (QA/QC), wind turbine inspection, and other specialized services. These offerings are specifically designed to meet the needs of utility-scale projects, ensuring the highest levels of accuracy and efficiency at every stage of the wind energy project's life.

Contact us if you require further details.